Note that the FM Sweep routine was first designed to generate a stimulus from a single DSS. There are now actually 2 DSS modules in operation on each of our computers. These DSS's have been used for some time by various other stimulus generation routines (such as the Tone Pips routine described below) which offer the option of presenting the stimulus from one DSS or the other, or from both of them simultaneously. This option has now been included in the FM Sweep routine. The user can choose DSS 1, 2, or both by specifying the DSS option as 1, 2, or 3, where 3 means both DSS's will present the stimulus.
While it is possible to program the 2 separate DSS's with different parameters, (see for example, the Tone Pips stimulus option), I decided to keep things simple in the FM Sweep routine and require that both DSS's operate using a single set of parameters that are defined by the user choices in the current FM Sweep menu. If there is substantial interest in a sweep search program that would offer different stimulus parameters for each DSS, then a separate program for this will have to be developed. It would necessitate a completely new menu and probably operate a bit differently. For now, however, this FM sweep routine will allow for the use of either or both DSS's, and will function much like the single DSS version did.
The parameters which determine the nature of the stimulus and of the graphical display of the PST histogram are accessible to the user by means of the following menu. In this example, the frequency of the stimulus sweeps from 100 Hz to 40000 Hz in 2.00 seconds, is held at 40000 Hz for 0.0 seconds, sweeps back down to 100 Hz in 2.0 seconds, and is held there for 0.0 seconds. The PST histogram has 200 bins. Note that the DSS parameter is 3, indicating that both DSS's will present the stimulus.
FREQLO = 100 Hz FREQHI = 40000 Hz SWR = 19950.00 Hz/sec TRISE = 2.00 sec TDWELL = 0.00 sec DSS (1,2,3=both): 3 SPL = 70 dB CORRECT SPL? y SPLCLIP = 10 dB NBINS = 200 BINW = 399.00 Hz AVEFILTER = 0 COMBINS = 0 NREPS = 10 UETCHAN = 0 UETCHAN2 = -1 MAXSPL1 = 131 dB * ATTEN1 = 61 dB DACBITS1 = 14 MAXSPL2 = 126 dB * ATTEN2 = 56 dB DACBITS2 = 14 g=^G=Go p=^P=Pause c=Clear e=^Z=Exit d=Screen Dump, t=Final ScreenDump w=Dset(newname), u=Dset(inc unit#), x=Dset(inc seq#) The parameters defining the stimulus waveform include: FREQLO lowest frequency (Hz) FREQHI highest frequency (Hz) TRISE rise time (sec) TDWELL dwell time (sec) SWR sweep rate (Hz/sec) SWR=(FREQHI-FREQLO)/TRISE NREPS total number of sweepsBecause many of these parameters are dependent on one another, a change in one of them can cause a change in others, depending on which of the others are held constant. Some conventions have been chosen to govern the way other parameters are updated whenever any one of them is changed by the user. The following table summarizes this:
Parameter Parameters Parameters that changed by updated retain old value the user FREQLO SWR FREQHI, TRISE, TDWELL FREQHI SWR FREQLO, TRISE, TDWELL SWR TRISE FREQLO, FREQHI, TDWELL TRISE SWR FREQLO, FREQHI, TDWELL TDWELL ---- FREQLO, FREQHI, TRISE, SWR
The sound pressure level is specified with the parameter SPL. Since the phone(s) used in any given experiment will, in general, maintain different sound pressure levels at different frequencies, there is a feature built into the DSS to correct for these different levels. As a result of the SPL correction, the corrected waveform will lose some of its resolution -- 1 bit of resolution for every 6 dB of correction that is done. The parameter SPLCLIP is used by the system as a limit of the amount of SPL correction to be made at any frequency. For more information about this important concept, please see the detailed description of SPL correction, which also discusses related parameters and shows a sample graph of an SPL calibration curve.
An additional feature of the FM Sweep routine is that the user can now specify 2 different input channels for the collection of spikes through the UET (Unit Event Timer). In the old version of the program, only data coming in through channel 0 of the UET was processed. The UET does have 16 input channels, numbered 0 through 15. Channel numbers 2, 3, and 6 are reserved for internal signals, but the user could connect data inputs to any of the other 13 channels. The current FM Sweep routine will process data from 2 separate input channels, and the user must specify the numbers of the 2 channels to be used. The menu parameters UETCHAN and UETCHAN2 are used for this.
While the stimulus is being presented, the neuronal data collected through each of the specified UET input channels is used to generate a PST histogram. Both histograms are displayed, using the same scale, on the current graphics device. The histogram corresponding to the 1st input channel (UETCHAN) is plotted as solid vectors, and that corresponding to the 2nd channel (UETCHAN2) is plotted as dashed vectors.
If only one UET input channel is being used, then the user should set either UETCHAN or UETCHAN2 to the value of that channel number, and set the other channel parameter to -1. In any case, a channel number of -1 means no input channel and therefore no data to be displayed.
The histogram is updated after approximately every sweep. The parameters that define the display include:
To run the FM Sweep stimulus, first specify all parameters to the desired values. The arrow keys on the keyboard are used to move around in the menu. (Note that when the program is started up, the parameters are set to the values they had during the previous run of FM Sweep.) To start the stimulus, type 'g', 'G', or CTRL-G. The FM sinusoid is then presented, sweeping through the appropriate frequencies, and repeating this sweep for the specified number of repetitions. The PST histogram is updated as often as possible. After NREPS repetitions, the stimulus stops, the histogram is cleared, and the program automatically restarts the stimulus for another NREPS sweeps. This will continue until the user stops it.
The following commands are available to the user: g, G, or CTRL-G Start or restart stimulus p, P, or CTRL-P Stop stimulus, stay in FM sweep menu e, E, or CTRL-Z Stop stimulus, return to SER main menu c or C Clear histogram and restart the stimulus d or D Dump current histogram display to printer t or T Dump final (NREPS) histogram to printer w or W Save current data, specify data set name u or U Save current data, increment unit # x or X Save current data, increment sequence #
Note that the user can change any menu parameter while the stimulus is running, simply by typing in the new value followed by the RETURN key. (Note that a new feature allows one to type any of the 4 arrow keys instead of the RETURN key; in this case, the parameter will be accepted, and the cursor will move one place in the appropriate direction.) When this is done, the stimulus in progress is stopped and the new stimulus is started. To change more than one menu item, it is usually faster to type p or CTRL-P first, change the parameters, then hit g or CTRL-G to restart.
Invalid parameter settings sometimes cause the stimulus to stop. The user must change the appropriate parameter(s), then type 'g' or CTRL-G to restart the stimulus.
To store the response data from the current series of NREPS sweeps, the user can type 'w', 'u', or 'x'. Each of these commands stores the data for the entire series of sweeps. The only difference between the 3 commands is how the name for the new data set is chosen. Each command displays the name of the mort recently stored data set. The 'w' command prompts the user to type in a new name for the data set to be stored. The 'u' or the 'x' command will try to automatically create a new data set ID name. They look at the previous name, which is understood to have the format 'unit#-sequence#', preceded by an optional string of characters. For example, a valid name would be abc100-12, where the unit number is 100 and the sequence number is 12. The 'u' command will increment the unit number, and the 'x' command will increment the sequence number. If the previous data set name is not in this format, then each of the commands will prompt the user to type in a new data set id name.
The data for a series of sweeps of the the FM stimulus are stored with the data set type name SRFM, which will distinguish it from data collected during one of the other stimulus options. The schema name for each data set is sch016.
Here is an Example of the PST Histogram Display for FM Sweep.
See also the general description of the
SER program.
See also the descriptions of the other SER stimulus options:
Tone Pips,
Clicks,
Noise,
Dual Tones
jane@neurophys.wisc.edu